It is necessary to use low-leak, high-insulation relays for the relays on the signal paths in microsignal measurement. The reed relay according to JP Laid-Open (Kokai) Patent 2001-14,994, FIG. 5, is known as this type of relay and is shown in FIG. 7 as reed relay 500. A reed switch 501 is supported inside an electrostatic shield pipe 503 by bushings 502a and 502b made from a high insulator, and this electrostatic shield pipe 503 is disposed in the cylindrical hollow part of a coil bobbin 504. A space 509 is formed between the inside wall of coil bobbin 504 and the outside wall of electrostatic shield pipe 503 where coil bobbin 504 and electrostatic shield pipe 503 contact one another by disposing projections 508a and 508b at the open ends of the hollow part of coil bobbin 504. As a result, the shield heat generated by a coil 505 wrapped around coil bobbin 504 is hard to be transmitted to electrostatic shield pipe 503. Thus, this makes it possible to reduce a heat-stimulated electrical current flows between bushings (502a and 502b) and electrostatic shield pipe 503, when joule heat is transferred to these bushings 502a and 502b of a conventional reed relay and, therefore, the offset current that flows between relay ends 517a and 517b and the respective bushings 502a and 502b is reduced. Nevertheless, there is a demand for reed relays that have an even further reduced heat-stimulated electrical current as a result of the developments being made in measurement technology.
On the other hand, FIG. 3 in JP Laid-Open (Kokai) Patent Sho 59[1984]-71,227, FIG. 3, cites a reed relay with an electrostatic shield pipe that does not have bushings. This is shown in FIG. 8 as reed relay 700. That is, a contact part 3 with a reed piece 1 passes through a guard pipe 21 and both ends of this reed piece 1 are supported by studs 9. Here, the effect of heat-stimulated electrical current on the bushing is not taken into consideration. Nevertheless, in order to maintain insulation performance, contact part 3 with the reed piece must not touch guard pipe 21. Therefore, it is necessary to very carefully and precisely adjust the height of the studs when mounting this reed relay 700, and this increases production cost. Consequently, there is a need for technology that simplifies the mounting of reed relay 700.
As noted with regard to FIG. 6 in JP Laid-Open (Kokai) Patent Hei 8[1996]-279,314, FIG. 6. the insulation member (bushing) that supports a reed switch 34 inside a cylindrical conductor 37 is placed between conductors of different potentials; therefore, it is a known fact that a long settling time is needed prior to measurement because of the effect of dielectric absorption.
A problem which the present invention is intended to solve is to provide an inexpensive reed relay for microsignals that does not have bushings supporting the reed in order to avoid the above-mentioned problems caused by bushings mechanically supporting the reed of a reed relay, and an inexpensive mounting method therefor.
Another problem which the present invention is intended to solve is to provide a reed relay for microsignals having a mechanism for which the bushings no longer support the reed once the relay body is anchored whereby initially bushings that support the reed of a reed switch are temporarily anchored to an electrostatic shield pipe or coil bobbin during reed relay production and then the reed relay is mounted on a substrate, and further, the reed is anchored to the substrate, with or without studs, and the like, as well as a mounting method therefor and a bushing thereof.
Therefore, the object of the present invention is to provide a reed relay for microsignals, a mounting method, and a bushing that are capable of solving the above-mentioned problems. This object is accomplished by the combination of characteristics according to the independent claims. The subordinate claims give other preferred embodiments of the present invention.